1、BRITISH STANDARD BS3730-2: 1982 Assessment of departures from roundness Part2: Specification for characteristics of stylus instruments for measuring variations in radius (including guidance on use and calibration) UDC 531.717.2:621.7.08BS3730-2:1982 This British Standard, having been prepared under
2、the directionof the Mechanical Engineering Standards Committee, was published underthe authority of the BoardofBSI and comes intoeffecton 31 December1982 BSI 07-1999 First published June1964 First revision December1982 The following BSI references relate to the work on this standard: Committee refer
3、ence MEE/69 Draft for comment 81/73683 DC ISBN 0 580 12967 5 Cooperating organizations The Mechanical Engineering Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: Associated Offices Technical Committee Department of Trade
4、(Marine Division) Association of Consulting Engineers Department of Transport Association of Hydraulic Equipment Electricity Supply Industry in England and Manufacturers Wales Association of Mining, Electrical and Energy Industries Council Mechanical Engineers Engineering Equipment Users Association
5、 British Compressed Air Society Federation of Manufacturers of Construction British Constructional Steelwork Equipment and Cranes Association Health and Safety Executive British Electrical and Allied Manufacturers Institution of Gas Engineers Association (BEAMA) Institution of Mechanical Engineers B
6、ritish Gas Corporation Institution of Plant Engineers British Internal Combustion Engine Institution of Production Engineers* Manufacturers Association Lloyds Register of Shipping British Pump Manufacturers Association London Transport Executive British Steel Corporation Machine Tool Industry Resear
7、ch British Steel Industry Association British Valve Manufacturers Association Ltd. Ministry of Defence* Chartered Institution of Building Services National Coal Board Crown Agents for Oversea Governments Oil Companies Materials Association and Administrations Process Plant Association Department of
8、Industry (Mechanical Society of Motor Manufacturers and Traders Engineering) Limited Department of Industry (National Telecommunication Engineering and Engineering Laboratory) Manufacturing Association (TEMA) Department of the Environment (PSA) Water-tube Boilermakers Association The organizations m
9、arked with an asterisk in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this British Standard: Gauge and Tool Makers Association University of Salford Production Engineering Research Association University of Warwi
10、ck of Great Britain Coopted member Scientific Instrument Manufacturers Association Amendments issued since publication Amd. No. Date of issue CommentsBS3730-2:1982 BSI 07-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Instruments 1 Appendix
11、A Departure from roundness of the measured profile of the workpiece 4 Appendix B Use of the instrument 7 Appendix C Calibration 10 Appendix D Determination of systemmatic errors of rotation 12 Appendix E Determination of least squares centre and circle 13 Appendix F Rules for plotting and reading po
12、lar graphs 16 Figure 1 Spherical stylus 1 Figure 2 Cylindrical stylus 1 Figure 3 Toroidal (hatchet) stylus 1 Figure 4 Oroidal stylus 2 Figure 5 Typical transmissions showing rate of attenuation given by two independent CR networks of equal time constant 3 Figure 6 Assessment of roundness from least
13、squares centre (Z q ) 4 Figure 7 Assessment of roundness from minimum zone centre (Z z ) 5 Figure 8 Assessment of roundness from centre of minimum circumscribed circle (Z c ) 6 Figure 9 Assessment of roundness from centre of maximum inscribed circle (Z i ) 7 Figure 10 Effect of eccentricity 8 Figure
14、 11 Effect of inclination of workpiece axis 8 Figure 12 Conical surface 8 Figure 13 Toroidal surface 8 Figure 14 Effect of roughness texture 9 Figure 15 Effect of stylus radius when in contact with surface 10 Figure 16 Traces by hatchet and sharp styli 11 Figure 17 Positioning of a stylus in a groov
15、e 11 Figure 18 Error due to stylus displacement 12 Figure 19 Illustrations of spindle errors and test piece out-of-roundness 14 Figure 20 Example of spindle error and test piece error 15 Figure 21 Determination of least squares centre and circle 15 Figure 22 Distortion due to polar plotting 16 Figur
16、e 23 Diametral variations 16 Figure 24 Radial variations 17 Figure 25 Error due to stylus displacement 17 Table 1 Limiting values of undulations per revolution 2 Publication referred to Inside back coverBS3730-2:1982 ii BSI 07-1999 Foreword This Part of this British Standard has been prepared under
17、the direction of the Mechanical Engineering Standards Committee. It takes account of discussions within ISO/TC57, Metrology and properties of surfaces, the results of which will be published as ISO4291. At the time of publication the technical content of this Part of this standard was in agreement w
18、ith the ISO draft. This standard together with Parts1 and3 supersedes BS3730:1964 which is now withdrawn. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Sta
19、ndard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to 18, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorpora
20、ted. This will be indicated in the amendment table on the inside front cover.BS3730-2:1982 BSI 07-1999 1 1 Scope This Part of this British Standard specifies the characteristics of contact (stylus) instruments based on the method of determining departures from roundness by measuring variations in ra
21、dius. It relates to the assessment of the departures from ideal roundness of a workpiece through the medium of a profile transformation, obtained under reference conditions, expressed with respect to any one of the following centres: a) centre of the least squares circle; b) centre of the minimum zo
22、ne circle; c) centre of the minimum circumscribed circle; d) centre of the maximum inscribed circle; NOTE 1Each of the foregoing centres may have its field of application. The position of the least squares centre can be calculated from a simple explicit formula given in Appendix E. Departures of rou
23、ndness from the measured profile, use of instrument, calibration and determination of systematic errors of rotation are dealt with in Appendix A to Appendix D, respectively. Appendix F gives rules for plotting and reading polar graphs. NOTE 2Reference conditions include the stylus, frequency limitat
24、ions of an electric wave filter (if used), permissible eccentricity of the graphic or digital representation of the profile (generally1/7 to1/15 of its mean radius, see Appendix F) and the position of the measured section or sections relative to some feature of the workpiece. NOTE 3The titles of the
25、 publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS3730 the definitions given in BS3730-1 apply, together with the following. overall instrument error the difference between the value of the parameter indicated, displayed
26、or recorded by the instrument and the true value of the parameter. The value of this error is determined by measuring a test piece 3 Instruments 3.1 Instrument types and general requirements 3.1.1 General. Instruments of the stylus type employed for the determination of departures from ideal roundne
27、ss shall be one of the following types: a) a stylus and transducer rotating round a stationary workpiece; or b) a rotating workpiece engaged by a stationary stylus and transducer. NOTEBy the character of the output information, instruments for the measurement of roundness fall into two groups: a) pr
28、ofile recording; b) direct display of the values of the parameters. Both groups can be combined in one instrument. Stylus instruments shall comply with3.1.2 to3.1.4. 3.1.2 Stylus types and dimensions. The surface characteristics of the part under examination are of primary importance in the choice o
29、f stylus and variations to comply with different requirements, depending upon the nature and magnitude of the irregularities that are to be taken into account, shall be as shown in Figure 1 to Figure 4 (see Appendix A). NOTENo order of preference is implied by the order of Figure 1 to Figure 4. Figu
30、re 1 Spherical stylus Figure 2 Cylindrical stylus Figure 3 Toroidal (hatchet) stylusBS3730-2:1982 2 BSI 07-1999 The dimensions r and R of the various stylii shall be selected from the following values: 0.25mm, 0.8mm, 2.5mm and8mm. 3.1.3 Stylus static force. The force shall be adjustable up to0.25 N
31、and in use shall be adjusted down to the lowest value that will ensure continuous contact between the stylus and the surface being measured. 3.1.4 Instrument response for sinusoidal undulations. The range of periodic sinusoidal undulations per revolution (i.e.per360 ) of the workpiece to which the i
32、nstrument responds shall be terminated by values taken from Table 1. Table 1 Limiting values of undulations per revolution The response at the rated termination of the band shall be75% of the maximum transmission within the band except for1 undulation per revolution which represents direct mechanica
33、l coupling between input and output (see note5). The transmission characteristics of the filter shall be equivalent to those produced by two independent CR networks of equal time constant (see Figure 5). NOTE 1These curves show only the amplitude attenuation characteristics and do not take phase shi
34、ft into account. A phase corrected filter of known characteristics giving the same rate (or a higher rate) of attenuation may be used. NOTE 2When a filter attenuating high frequencies is required, the2-CR form will generally be acceptable, distortion of the transmitted profile due to phase shift of
35、the high frequencies relative to the low frequencies being generally unimportant. When a filter attenuating low frequencies is required, distortion due to phase shift may be more significant and have to be taken into account or avoided by using a phase corrected filter. NOTE 3It is necessary to dist
36、inguish clearly between the undulations per revolution (i.e.per360 ) of the workpiece and the response of electronic circuits in the instrument in hertz. The frequency in cycles per second (hertz) generated by the instrument will be given by: sinusoidal undulations per360 of the workpiece x revoluti
37、ons per second of the spindle. NOTE 4Eccentricity will count as1 undulation per revolution. A sinusoidal component of1 undulation per revolution will be found when the periphery of the workpiece is assessed from a centre other than the centre of the least squares circle. NOTE 5When electronic circui
38、ts of instruments are required to respond to down to1 undulation per revolution, they are often made responsive down to zero frequency (0Hz), this being a natural way of avoiding phase distortion and permitting calibration by static means. 3.2 Instrument error 3.2.1 Overall instrument error. The ove
39、rall instrument error, comprising systematic and random components from the spindle error, electric noise, vibration, magnification, etc., shall be expressed as a percentage of the upper limiting value of the measuring range used. 3.2.2 Errors of rotation of the instrument 3.2.2.1 General. The follo
40、wing errors of rotation shall be determined under reference conditions at assigned positions of measurement: a) Radial instrument error: the value of roundness parameter that would be indicated by the instrument when measuring a perfectly round and perfectly centred section of a test piece, in a dir
41、ection perpendicular to the reference axis of rotation; b) Axial instrument error: the value derived from the zonal parameter displayed by the instrument when measuring on a perfectly flat test piece set perfectly perpendicular to the reference axis of rotation. NOTEThe components of errors of rotat
42、ion are vector quantities and should not therefore be algebraically added to the measured value of a roundness parameter in an attempt to allow for errors of rotation. 3.2.2.2 Statements of errors of rotation. The displacements that the rotating member can exhibit, within the confines of its bearing
43、s, shall be divided into combinations of: a) radial displacements parallel to itself; b) axial displacements parallel to itself; c) tilt. Figure 4 Ovoidal stylus Filters transmitting from1 undulation per revolution up to Filters rejecting below undulations per revolution 15 50 150 500 1 500 undulati
44、ons per revolution 50 100 500 BS3730-2:1982 BSI 07-1999 3 As the magnitude of the radial instrument error measured at the stylus depends on the position of the measurement plane along the axis of rotation and the magnitude of the axial instrument error depends on the radius at which the flat test pi
45、ece is measured, the axial and radial positions selected for test shall be stated. The radial instrument error shall be expressed at two stated and well separated positions along the axis, or at one position together with the rate of change of the radial instrument error along the axis. The axial in
46、strument error shall be expressed on the axis and at one stated radius. Figure 5 Typical transmissions showing rate of attenuation given by two independentCRnetworks of equal time constantBS3730-2:1982 4 BSI 07-1999 Appendix A Departure from roundness of the measured profile of the workpiece In this
47、 Part of this standard, the departure from ideal roundness is assessed as the difference between the largest and the smallest radii of the measured profile of the workpiece, measured from one or other of the following centres. a) Least squares centre (LSC): the centre of the least squares mean circl
48、e (see Figure 6). b) Minimum zone centre (MZC): the centre of the minimum zone circle (see Figure 7). c) Minimum circumscribed circle centre (MCC): the centre of the minimum circumscribed circle for external surfaces (see Figure 8). d) Maximum inscribed circle centre (MIC): the centre of the maximum
49、 inscribed circle for internal surfaces (see Figure 9). The largest and smallest radius, in each case, is commonly used to define a concentric zone. The kind of zone may be designated by the letter z, together with a suffix denoting its centre. For the purposes of this standard the following suffices are used: e) least squares: suffix q, thus Z q ; f) minimum width: suffix z, thus Z z ; g) minimum circumscribed: suffix c, thus Z c ; h) maximum inscribed: suffix i, thus Z i . NOTEThe use of circles dr
